§ 155.056 SEWER FACILITIES.

   (A)   General requirements. The applicant shall install sanitary sewer facilities in a manner prescribed by the Uniform Standard Details and Specifications and the City Engineer.

   (B)   Public sewerage required. For all subdivisions, sanitary sewer facilities shall connect with public sanitary sewage system. Sewers shall be installed to serve each lot and to grades and sizes required by the Uniform Standard Details and Specifications and the City Engineer.

   (C)   Mandatory connection to public sewer system. If a public sanitary sewer is installed within 200 feet of an individual lot, the owner thereof shall be required to connect to the sewer for the purpose of disposing of waste, and it shall be unlawful for any owner or occupant to maintain upon any property the use of an individual sewage disposal system thereafter.

   (D)   Design criteria for sanitary sewers.

      (1)   Design factors.

         (a)   Sanitary sewer systems should be designed for the ultimate drainage basin population. Consideration should be given to current zoning regulations, and should be given to current zoning regulations, and approved planning and zoning reports where applicable. Sewer capacities should be adequate to handle the anticipated maximum hourly quantity of sewage and industrial waste together with an adequate allowance for infiltration and other extraneous flow. The unit design flows presented hereinafter should be adequate in each case for the particular type of development indicated. Sewers shall be designed for the total tributary area using the following criteria:

One- and two-family dwellings	.02 cfs/acre*
Apartments, townhouses, condominiums
One- and two-story	.02 cfs/acre
Three- though six-story	.03 cfs/acres
Commercial - small stores, offices and miscellaneous businesses	.02 cfs/acre
Shopping centers	.02 cfs/acre
Industrial buildings	As directed by the City Engineer
Note to table * Cubic feet per second per acres

 

         (b)   These design factors shall apply to watersheds of 300 acres or less. Design factors for watersheds larger than 300 acres and smaller than 1,000 acres shall be computed on the bases of a linear decrease from the applicable design factor for an area of 300 acres to a design factor for .01 cfs/acre for an area of 1,000 acres unless otherwise directed by the City Engineer. Design factors for watersheds larger than 1,000 acres shall be .01 cfs/acre unless otherwise directed by the City Engineer.

      (2)   Maximum size. The diameter of sewers proposed shall not exceed the diameter of the existing or proposed outlet, whichever is applicable, unless otherwise approved by the City Engineer.

      (3)   Minimum size. No public sanitary sewer shall be less than eight inches in diameter.

      (4)   Minimum slope. All sewers shall be designed to give mean velocities, when flowing full, of not less than 2.0 feet per second. All velocity and flow calculations shall be based on the Manning Formula using an “N” value of 0.013. The slopes shall be minimum for size indicated. Exceptions to these minimum slopes shall be made at the upper end of lateral sewers serving less than 30 houses. The sewers shall have a minimum slope of 0.76%. Where lateral sewers serve less than ten houses, the minimum slope shall be not less than 1%. Table 3, below, lists minimum slopes for various sewer sizes:

Table 3
Minimum Slope by Sewer Size
Sewer Size (in Inches)	Minimum Slope in Feet per 100 Feet
8	0.33
10	0.24
12	0.19
15	0.14
18	0.11
21	0.093
24	0.077
Source: BRW, Inc., 1987; Arizona Department of Health Services Bulletin Number 11

 

      (5)   Alignment. All sewers shall be laid with straight alignment between manholes, unless otherwise directed or approved by the City Engineer.

      (6)   Manhole location. Manholes shall be installed at the end of each line; at all changes in grade, size, or alignment; at all intersections; and at distances not greater than 400 feet for sewers less than 18 inches, and 500 feet for sewers 18 inches in diameter and larger.

      (7)   Manholes. The difference in elevation between any incoming sewer and the manhole invert shall not exceed 12 inches except where required to match crowns. The use of drop manholes will require approval by the City Engineer. The minimum inside diameter of the manholes shall conform to those specified by the City Engineer. Inside drop manholes will require special considerations; however, in no case shall the minimum clear distance be less than that indicated above. When a smaller sewer joins a larger one, the crown of the small sewer shall not be lower than that of the larger one. The minimum drop through manholes shall be 0.2 feet.

      (8)   Sanitary sewer locations. Sanitary sewers shall be located within street or alley rights-of-way unless topography dictates otherwise. When located in easements on private property, access shall be provided to all manholes. A manhole shall be provided at each street or alley crossing. End lines shall be extended to provide access from street or alley rights-of-way where possible. Imposed loading shall be considered in all locations. Not less than three feet of cover shall be provided over top of pipe in street and alley rights-of-way or three feet in all other areas.

      (9)   Cleanout and lampholes. Cleanouts and lampholes will not be permitted.

      (10)   Water supply interconnections. There shall be no physical connection between a public or private potable water supply system and sewer which will permit the passage of any sewage or polluted water into the potable supply. Sewers shall be kept removed from water supply wells or other water supply sources and structures.

      (11)   Relationship of sewers to water mains. A minimum horizontal distance of six feet shall be maintained between parallel water and sewer lines. At points where sewers cross water mains, the sewer shall be constructed of cast iron pipe or encased in concrete for a distance of ten feet in each direction from the crossing, measured perpendicular to the water line. This will not be required when the water main is at least two feet above the sewer line.

      (12)   Extraordinary situations. These design criteria are not intended to cover extraordinary situations. Deviations will be allowed and may be required in those instances where considered justified by the City Engineer.

(Prior Code, § 15-4-7) (Ord. O88-06-007, passed 10-13-1988)